Welcome to HVAC-Talk.com, a non-DIY site and the ultimate Source for HVAC Information & Knowledge Sharing for the industry professional! Here you can join over 150,000 HVAC Professionals & enthusiasts from around the world discussing all things related to HVAC/R. You are currently viewing as a NON-REGISTERED guest which gives you limited access to view discussions

To gain full access to our forums you must register; for a free account. As a registered Guest you will be able to:

Participate in over 40 different forums and search/browse from nearly 3 million posts.

I have been slowly growing my business for about 4 years and am just now buying a combustion analyzer. I know that you guys are probably going to tear me up and call me a hack for not owning one yet, but I've been accumulating other tools and figured I could get by with timing the meter and some other measurements. So, when you're done with any insults you want to toss out there could you tell me how you are getting flue gas analysis on systems with B-Vent? Or for that matter, how about the 90 plus systems? I don't want to breach the integrity of the vents.

I didn't know it was ok to make a test hole in a flue.
I'm sure my boss would like to have info on this
(knowing him, he already knows it..... its hard for me to teach him anything. He's a freakin walking encylopedia)
Can you have bacharach post info on this on their website.
Unless its there already and I haven't seen it.
If its there, then give me a link.

Also, you got any suggestions on how to seal the holes?

Being a tech, I'll need something that sets up 'really fast'. Actually I need something that can be removed for
future testing. We do a flue gas analysis on all our safety and effeciency contracts. Do you know of any products that are UL listed for this?

sealing Cat IV venting

I wouldn't seal holes in PVC with foil tape. It may stick now but over time the acrylic adhesive will break down and it will lose its grip. Since this pipe is under positive pressure, you have something trying to poke its way out or pry it off. Also, the very acidic condensate will eat right through that foil.

If you're gonna drill it, seal it with something that's air tight, liquid tight, and acid resistant. Then test it for leaks using a chemical smoke puffer, soap bubble soln., and a CO meter. The smoke will show you pin hole leaks. You can try soap bubbles but generally the high pressure will simply blow it away without forming a bubble. The CO should be self explanatory.

One tip, don't drill where condensate will probably drain to the hole.

Second tip: permanently mount a fitting with a cap. Record the vent pressure as a benchmark.On B-vent, you can get a draft reading. Should anything go wrong with the pipe joints or the blower, the pressure will change. With PVC, a blocked vent will usually read high. Here you'r looking for a change and not so much one specific number. Before cementing the PVC to the appliance collar it is always a good idea to run a quick pressure test. Seal the end towards the appliance with a cap cemented on that will be cut off later. Install a test plug with a Schraeder valve at the discahrge and put a few pounds of air in it. Read your pressure off the test plug. You can puff the joints if the gauge starts dropping.

When sealing B-vent, make sure you work some silicone in btw the inner and outer walls so you don't lose the seal. OF course, since most vent connectors are single walled galv. you can drill this and seal with a button plug for easy removal. Since this pipe should be under negative pressure, any micro leaks should act as a venturi and entrain room air. However, with Cat. IV fan assisted furnaces, you'll want a tighter plug so it doesn't blow by.

I've scanned the letters from the B-vent manufacturers but I'll be damned if I can find them this eve. I just emailed one of the other trainers I work with asking him to email them to me (again). As soon as he does I'll put them up on the training website and post the link.

B-vent should be under negative pressure, a small test hole isnt going to make a big deal. If worst comes to worst, get a 1/4 threaded bolt and cut it to 1/4" long and screw it in the hole when your done with the test.

PVC vents can handle a dollop of standard silicone over the test hole.

For those wanting 'hard copy' documentation of the letters from B-Vent manufacturers allowing the drilling of their products - I finally found the files this am and finally remembered how to put them up on the website (it's been a while...).